1. Field of the Invention
The present invention relates to a hydrodynamic bearing assembly and a spindle motor including the same.
2. Description of the Related Art
A hard disk drive (HDD), an information storage device, reads data stored on a disk or writes data to a disk using a read/write head.
A hard disk drive requires a disk driving device capable of driving the disk. In the disk driving device, a small spindle motor is commonly used.
This small spindle motor uses a hydrodynamic bearing assembly. A lubricating fluid is interposed between a shaft and a sleeve of the hydrodynamic bearing assembly, such that the shaft is supported by fluid pressure generated in the lubricating fluid.
In this case, two dynamic pressure generation grooves are generally formed in upper and lower portions of the shaft or the sleeve in an axial direction in order to form at least two bearing axes, thereby allowing the shaft to rotate in a stable position. That is, at the time of driving of the motor, the lubricating fluid stored in the upper and lower portions of the dynamic pressure generation groove is concentrated on the dynamic pressure generation groove, such that at least two bearing axes are formed.
However, in the case in which the lubricating fluid between the two dynamic pressure generation grooves is excessively pumped in one or in two directions due to an error in manufacturing, vibrations, an external impact, or the like, an amount of the lubricating fluid in a bearing clearance between the two dynamic pressure generation grooves may suddenly be insufficient, such that negative pressure may be generated. In the case that negative pressure is generated, noise, vibrations, or the like, may be generated in the motor, such that the motor may be unstably operated.
Further, when the negative pressure is generated, air bubbles are formed in the lubricating fluid or existing bubbles are enlarged, such that motor performance may be deteriorated.
Therefore, research into a new structure of a bearing assembly capable of improving operational performance of a motor and preventing the generation of negative pressure has been urgently demanded.
The following Related Art Document has disclosed a spindle motor using a hydrodynamic bearing and suggests a structure for preventing the generation of negative pressure.